Excited States from State-Specific Orbital-Optimized Pair Coupled Cluster.
Excited States from State-Specific Orbital-Optimized Pair Coupled Cluster.
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特定状态轨道优化对耦合团簇的激发态。
DOI：
10.1021/acs.jctc.1c00348
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发表时间：
2021-08-10
影响因子：
5.5
通讯作者：
Loos PF
中科院分区：
文献类型：
--
作者：
Kossoski F;Marie A;Scemama A;Caffarel M;Loos PF
对耦合团簇加倍(PCCD)方法(其中激发流形被限制为电子对)具有一系列有趣的特征。其中，它提供的基态能量非常接近双占据组态相互作用(DOCI)所获得的能量，但具有多项式成本(与后者的指数成本相比)。在这里，我们通过探索线性H4分子的对称解离来讨论这种相似性是否适用于激发态。当使用基态Hartree-Fock(HF)轨道时，PCCD和DOCI激发态能量不匹配，这一特征被分配给较差的HF参考。相反，通过专门为每个激发态优化PCCD水平上的轨道(oo-PCCD)，PCCD和DOCi之间的差异减少了1到2个数量级。因此，PCCD和DOCI方法仍然为激发态提供类似的能量，但只有在采用适当的特定状态轨道的情况下才能提供。我们还评估了PCCD方法是否可以用于直接瞄准双激发态，而不必求助于运动方程(EOM)形式。在我们的Δoo-PCCD模型中，激发能是从基态和目标激发态的Oo-PCCD计算之间的能量差中提取的。对于由CH+、BH、氮氧基、亚硝基和甲醛双激发态组成的集合，我们发现Δoo-PCCD提供了相当精确的激发能量，其均方根偏差(相对于全组态相互作用结果)低于CC3，与EOM-CCSDT相当，这两种方法的计算量要高得多。
The pair coupled cluster doubles (pCCD) method (where the excitation manifold is restricted to electron pairs) has a series of interesting features. Among others, it provides ground-state energies very close to what is obtained with doubly occupied configuration interaction (DOCI), but with a polynomial cost (compared with the exponential cost of the latter). Here, we address whether this similarity holds for excited states by exploring the symmetric dissociation of the linear H4 molecule. When ground-state Hartree–Fock (HF) orbitals are employed, pCCD and DOCI excited-state energies do not match, a feature that is assigned to the poor HF reference. In contrast, by optimizing the orbitals at the pCCD level (oo-pCCD) specifically for each excited state, the discrepancies between pCCD and DOCI decrease by 1 or 2 orders of magnitude. Therefore, the pCCD and DOCI methodologies still provide comparable energies for excited states, but only if suitable, state-specific orbitals are adopted. We also assessed whether a pCCD approach could be used to directly target doubly excited states, without having to resort to the equation-of-motion (EOM) formalism. In our Δoo-pCCD model, excitation energies are extracted from the energy difference between separate oo-pCCD calculations for the ground state and the targeted excited state. For a set comprising the doubly excited states of CH+, BH, nitroxyl, nitrosomethane, and formaldehyde, we found that Δoo-pCCD provides quite accurate excitation energies, with root-mean-square deviations (with respect to full configuration interaction results) lower than those of CC3 and comparable to those of EOM-CCSDT, two methods with a much higher computational cost.
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影响因子：
3.7
作者：
Boguslawski, Katharina;Tecmer, Pawel;Van Neck, Dimitri
通讯作者：
Van Neck, Dimitri
影响因子：
4.4
作者：
Booth, George H.;Thom, Alex J. W.;Alavi, Ali
通讯作者：
Alavi, Ali
影响因子：
5.5
作者：
Burton, Hugh G. A.;Gross, Mark;Thom, Alex J. W.
通讯作者：
Thom, Alex J. W.
影响因子：
4.4
作者：
Boguslawski, Katharina
通讯作者：
Boguslawski, Katharina
影响因子：
4.4
作者：
Boguslawski, Katharina;Tecmer, Pawel;Van Neck, Dimitri
通讯作者：
Van Neck, Dimitri